Hi Evie, what synchronicity! Excellent promotional work: bringing in a poster and a donated book. You actually have an easy venue. First of all, you won't be alone, so the pressure won't be all on you. Second of all, you get to read, versus having to do public speaking. My tip would be to practice, practice, practice, out loud, or even into a tape recorder. You may need to time yourself. I'd try to find a piece without too much dialogue unless you are a pro at changing tone, inflection, and voice. Readings are great! They are fun, you have a captive audience, and you don't have to memorize. Way to go!